1. Field of the Invention
This invention relates to the method of making of retractile cords, and more particularly, to methods for the automatic manufacture of telephone cords wherein cordage is drawn from a supply, is fed into an apparatus and is conveyed through a plurality of the apparatus so that it emerges therefrom as a retractile cord adaptable for subsequent end finishing.
2. Description of the Prior Art
Retractile telephone cords, commonly referred to as spring cords, are widely used in the communications industry. For example, retractile cords are used to connect the handset of a telephone instrument to the telephone base. The spring cord is manufactured with the major portion thereof in the form of a compact helical cord, which may be extended by slight tension and which will return to the compact form when the tension is relieved.
The process of manufacturing spring cords by manual operation is well known and is described, for example, in U.S. Pat. No. 3,024,497 issued on Mar. 13, 1962 to E. C. Hardesty and D. L. Myers; the structure of the retractile cord is shown, for example, in U.S. Pat. No. 3,037,068 issued on May 29, 1962 to H. L. Wessel; and cord manufacturing apparatus is shown in E. L. Franke, Jr. U.S. Pat. No. 2,920,348 issued on Jan. 12, 1960, all incorporated by reference hereinto.
Generally, the manufacture of spring cords in the past has involved an operator who coils cordage from a fixed feed-in point onto a longitudinally moving mandrel after which the operator stacks a plurality of the mandrels in a rack which is conveyed in succession through an oven and a cooling chamber. Subsequently, the operator places each of the mandrels in an apparatus and then removes the cord from the mandrel while reversing the pitch of the helices of the cord to cause the spring cord to have a permanent and improved retractility.
Improved methods for stretching a spring cord by controlled varying amounts during helix reversing and overtwisting operations are disclosed in U.S. Pat. No. 3,087,199 issued on Apr. 30, 1963 to E. L. Franke, Jr. et al.
It is known to remove heat-treated spring cords from associated mandrels and to reverse the pitch of the helices of the coils by mounting a plurality of mandrels vertically and rotatably in a spaced-parallel array. A reciprocally movable carriage having a plurality of spindles rotatably mounted thereon is supported from a frame with each of the spindles aligned with an associated one of the mandrels. The carriage is moved from the mandrel to unwind the spring cords from the associated mandrels. Simultaneously, the spindles may be rotated in such a manner as to reverse the pitch of the helix of the spring cords being unwound from the mandrels.
As the carriage is moved relative to the mandrel to uncoil the cord, successive sections of the cord are moved axially, horizontally, and generally perpendicular to a stationary plate positioned between the mandrel and the carriage so that portions of the cord adjacent to the trailing end thereof are moved into and pulled through an associated slot formed in the plate. As the trailing end of the cord is disengaged from the mandrel, the last few convolutions of the cord spring together and expand radially on the mandrel-side of the plate thereby preventing the cordage from being pulled further through the slot. This is effective in retaining the last few convultions of the cords on the mandrel-side of the plate to maintain the cords unentangled and strung out between the spindle and the plate to facilitate removal. See U.S. Pat. No. 3,656,516 issued Apr. 18, 1972 in the name of E. C. Hardesty.
There have been attempts to construct an apparatus which may overcome the many manual steps involved in the well known techniques of making spring cords. For example, see U.S. Pat. Nos. 2,173,096, 2,525,285, 2,547,356, 2,718,660, 2,804,647. See also U.S. Pat. No. 2,898,630 issued Aug. 11, 1959 to G. P. Adams.
In U.S. Pat. No. 3,226,767, a leading end of cordage is attached to a mandrel which is then rolled along a magnetic track while winding convolutions on the mandrel. Subsequently, the mandrel is advanced through a heating zone, which comprises radiant heating elements or other heating means such as banks of infrared bulbs or facilities for induction heating of the mandrel. The mandrel is conveyed through a cooling zone and then to a reverse removing station whereat a released end of the coiled cordage is inserted into an unwinding mandrel with the mandrels driven in opposite directions to unwind the cord from one mandrel and reverse coil it onto the other. The reverse-coiled cord is removed from the mandrel by an axially sliding movement of the length toward and past the free end of the mandrel. See also U.S. Pat. No. 3,184,795, which interposes a blade-like member between adjacent ones of the convolutions being wound on a longitudinally moved mandrel to space the convolutions.
It has long been desired to provide a method which may be used to produce retractile cords at a high rate of production with the use of minimum floor space in order to realize manufacturing economies and to produce uniformly coiled heatset cords having uniform characteristics.